Morgan Stanley, meanwhile, has formed a committee, chaired by one of its top investment bankers, to look for ways to improve junior employees' working conditions, people familiar with the group said.

Across the financial-services industry, recruiting managers have begun selecting the next class of summer interns, and most will make their final decisions by next month.

Long hours and menial tasks are the norm for interns, according to interviews with two dozen current and former bank interns. They said they routinely put in 13 to 14-hour days and stayed in the office until early-morning hours about twice a week.

But with college students increasingly eschewing Wall Street for Silicon Valley and elsewhere, some bank executives are reconsidering this rite of passage, while others already have taken steps to ease conditions for young people.

Goldman Sachs in October said it formed a task force to improve the work-life balance for its youngest staff and announced reduced weekend work for analysts.

JP Morgan Chase last month told employees it would hire more junior staff to alleviate analysts' and associates' heavy workloads. It also is expanding a pilot programme to give junior bankers one optional "protected weekend" a month when they aren't expected to come into the office or respond to work phone calls and emails, according to a person familiar with the matter.

Related

Summer internships often lead to analyst positions, the junior-most investment banking staffers on Wall Street. Such jobs, which typically are cemented with two- or three-year contracts, are among the best paying for young people in the US.

The base salary for entry-level analysts is about $70,000 a year and annual compensation can shoot up to more than $140,000 with bonuses, said industry experts. Summer interns receive the same salary on a prorated basis.

The lavish pay comes with heavy lifestyle costs, former interns said. Interns typically are expected to report to work between 8:30 and 9:30 in the morning. But often, big assignments aren't handed out until the late afternoon or evening, requiring interns to stay late into the night, former interns said. They said they often spent regular business hours doing menial tasks or nothing at all.

"On a weekly basis, I worked 100-plus hours on average," said David Salsone, 29 years old, who interned in Morgan Stanley's investment banking group in 2012 in Menlo Park, Calif. Salsone served a stint in the military before attending college, so he says he was used to long hours.

"There were some nights I'd work up until a few hours before the next day would start. I'd go home, shower, shave and come back to work," he said. "And there were some days where you don't go home." Salsone has more recently set his sights on the technology industry. A Morgan Stanley spokesman declined to comment on Salsone's experience.

Morgan Stanley chief executive James Gorman has told groups of employees in recent months that he disagreed with rigid policies banning junior employees from working weekends, people familiar with the matter say. He has argued the restrictions could deprive employees of the opportunity to work on high-profile assignments.

Summer interns at Barclays in Hong Kong in 2011 say they had to get creative to find time for sleep. Exhausted from hours of nonstop work, the interns would sneak into a bathroom stall, plug headphones into their smartphones and set the alarm, in hopes of stealing a few precious minutes of shut-eye, according to several former interns who worked for the bank in the summer of 2011. Some dubbed it the "toilet nap."

A Barclays spokeswoman, while declining to discuss the specific incident, said: "We are constantly evaluating our analyst programme to ensure that it is a challenging and rewarding yet balanced experience."

Many interns come into the jobs expecting to be challenged and to make sacrifices. They want to work on high-profile deals where corporate clients ask for high-precision, deadline-sensitive work. And many said they view the positions as steppingstones to high-paying investment banking careers.

Internships in a few other industries are equally intense. In consulting and accounting, as well as the technology and energy sectors, internships often serve as summer-long recruiting tools for the firms, said Trudy Steinfeld, executive director of the New York University Wasserman Center for Career Development. The internships typically combine demanding work with team-building events, such as off-site leadership conferences.

Pat Pow-anpongkul, 26, who interned at Lehman Brothers in 2008, said during business hours his job was to provide news clippings to senior bankers. But come 6 pm, the work would start flooding in, he said, as senior bankers would ask for help with client-presentation materials that could take hours.

Pow-anpongkul said he would file a big document to the printing department around midnight, wait four hours for it to print and then walk it over to the senior banker's desk or, in some cases, have a courier send it to his house so he had it when he awoke.

"When you're a summer analyst, you're starving to do as much as you can because the more that you can prove, the more likely you are to get an offer," he said.

Pow-anpongkul now works in the technology industry in Silicon Valley for real-estate startup Trulia. A spokeswoman for Barclays, which bought parts of Lehman Brothers in 2008, declined to comment.

One veteran investment banker noted that many assignments given to interns or junior employees happen toward the end of the day because that is when executives have time to assess how the day went and how they can "get ahead of what is next."

Wall Street is looking at changes as many of the nation's top graduate and undergraduate business schools have reported a decline in the share of students interested in taking investment banking jobs. At Wharton, a top feeder for big banks, about 25% of undergraduate students went into investment banking in 2013, down from almost 41% in 2007.

But some students still picking investment banking are as hungry as ever.

"Only a certain percentage of people are going to get offers," said Shaun Khubchandani, who interned in Citigroup's investment banking division in 2010. "Some people were pushing themselves too much, to a point that wasn't even required by the group." A Citi spokeswoman declined to comment.

At Barclays, in a separate incident from the toilet naps, two former interns in Hong Kong said fellow interns had discovered that another intern had sometimes slept under his desk and washed up in the office bathroom the next morning, to save the time it would have taken to commute to the nearby residence hall where interns stayed.

"The well-being of all of our employees is a top priority," said the Barclays spokeswoman.

—Ben Wright and Justin Baer contributed to this article.

Write to Shayndi Raice at shayndi.raice@wsj.com and Lindsay Gellman at lindsay.gellman@wsj.com
-- This article was first published by The Wall Street Journal